1. Field of the Invention
The present invention relates to a stepping motor and a timepiece provided with the stepping motor.
2. Description of Related Art
A typical conventional stepping motor includes two coils and can rotate in both the normal and reverse directions under appropriate driving pulses applied to the coils.
For example, JP Hei05-006440 discloses a stepping motor including a bipolarly-magnetized round rotor magnet and a stator having two primary poles and a single secondary pole.
Unfortunately, the two coils of the conventional stepping motor are connected to a circuit all the time, resulting in a constant electrical loop between the coils.
When driving pulses are applied to one of the coils, the inductance occurs in the other coil in response to the rotation of the rotor. Such inductance obstructs the rotation of the rotor.
In other words, if driving pulses are applied to one of the coils alone, the reactance occurring in the other coil in response to the rotation of the rotor driven by the one coil obstructs the rotation of the rotor.
The reactance consumes the power supplied for rotating the rotor, so that the rotation of the rotor requires an additional amount of energy.